Nickel plating process



United States Patent NICKEL PLATIN G PROCESS Thomas B. Hoover and Thomas E. Zava, Oak Ridge, Tenn., assignors to the United States of America as represented. by the United, States Atomic Energy Commission No. Drawing. Application July 16, 1953 Serial No. 368,501

; Claims. (Cl. 117-107) Our ainvention v relates to an improved method and composition for plating nickel and. more particularly to an improvement in a, method; and composition for plating nickel by; the vapor decomposition. of nickel carbonyl [Ni(CO) in a mixture of nickel carbonyl vapor andiHgs.

Nickel plating is now extensively employed to provide decorative, andprotective coatings, particularly on steel.

Reference. is made to co-pending application, Nickel Plating. Process, filed July 16, 1953, SN. 368,502, by Thomas B. Hoover, which discloses. an unusually efiiqacious, improvement in a nickel carbonyl vapor process for: plating nickel which comprises providing a small amount of. H 8 in said nickel carbonyl vapor.

However, the method of the co-pending application, although requiring a, considerably lower reaction temperai t han earlier prior art methods, still requires a temperature ofat, least approximately 60 C. In, addition, an enclosed, heated reaction, chamber is necessary, and; materials whose surfaces decompose or are otherwise adversely, afiected at temperatures of 60 C. and above amctbepla e Fu thermor in Gasesi Chemical Engineering, l- 1-9 the following is stated:

Nickel carbonyl is a, strong reducing agent. Mixed with oxygen it; may explode violently. at temperatures as lowas 60, deg. C. This explains the thorough flushing: of

Metal Plating From Carbonyl vol. 56; October 1949, p.

. both carburator and, deposition chamber with inert gases beforeintroduction of Ni.(CO)

An object of our invention, therefore is to provide an improved; composition from which nickel. may beplated at. room temperature by vapor decomposition.

Another object of out invention is. to provide. an improve ncnt'in a vapor decomposition, nickel plating procaQsgQlllPlOYlIlg a mixture of nickel carbonyl vapor and H 5 whereinnoreaction chamber isrequired.

Still another object of; our invention is toprovide'an improved vapor decomposition method of plating nickel on thermally sensitive substances.

Another object of our invention is to provide an improved vapor decomposition method of plating nickel ,which is noneXPlosive.

Other objects and advantages of our invention will become apparent from the followingdetailed description and the appended claims.

Inaccordance with our invention, all the herein stated objects may be achieved and" an unexpected and striking improvement may be obtained in a vapor decomposition process of plating nickel employing a mixture of nickel carbonyl vapor and H 8, by providing in saidmixture a smallamount of at least one atmospheric oxidizing agent selected from the group consisting of O and H 0 vapor.

Employing our invention, we find, that for presently unexplainable reasons, nickel unexpectedly may be plated; out in an eminently satisfactory manner at room temperature. Consequently, no reaction chamber and associated heating means are required. As a result, an even wider Patented May 12, 1959 variety of materials may be plated with nickel than was possible by priormethods. Thus, relatively heat-sensitive materials such as certain kinds of papers, low melting thermoplastics, paraflins, waxes, etc., can be nickel plated. Furthermore, we find' that an electrically conducting, but very thin, transparent layer of nickel may be plated upon transparent materials. The latter discovery may be extremely valuable inproviding easily defrostable glass or plastic windows, particularly in airplanes.

Another advantage of our process, resides in the nonexplosive nature of the reaction mixture when mixed with oxygen. In the prior art, unusual precautions were practiced to prevent leakage of moisture or oxygen into the reaction zone from the atmosphere. However, explosion hazards are completely eliminated in our process, perhaps due to the relatively low temperature employed.

Suitable quantities of water vapor or oxygen for addition to the nickel carbonyl-H 8 mixture are from about 0.02% to about 1.5% by volume, the amount of inert carrier gas, if employed, or the nickel carbonyl, being correspondly reduced.

However, particularly satisfactory vapor are from about 0.02% to about 0.16% by volume while approximately 0.08% is generally preferred. Particularly satisfactory amounts of oxygen are from about 0.5% to about 1.5% while approximately 1% is preferred.

The oxygen or water vapor maybe added to our mixture from conventional industrial supply sources, while a portion or all of either agent could also be added from the ambient-atmosphere.

Suitable volume percentages of H 8 in the vapor mixture employed in our invention are from approximately 0.1% to approximately 1%, while approximately 0.2% is preferred. The reaction may be further catalyzed em ploying amounts of'H S in excess of 1%, but increased sulphur deposition may occur without a corresponding increase in the reaction rate.

Nickel carbonyl, which is a normal amounts of water relatively volatile liquid at through the liquid carbonyl at room temperature at a rate sufiicient to saturate it with carbonyl vapor. The volume percentage of Ni'(CO) may be varied by either adjusting the temperature of the liquid carbonyl through which the gas is bubbled, by varying the pressure under which; the carbonyl isvaporized, or by diluting a Ni(CO) vapor-H s-carrier gas mixture with additional carrier gas. However, the slight; improvement resulting from the latter procedures is insufiicient to justifythe additional effort. The exact percentage of Ni(CO) in the vapor mixture is not crltical and may'vary over a relatively wide range. Generally, vapor mixtures containing approximately 5% to, approximately-40,% Ni(CO) vapor, by volume, are suitable, while approximately 20% Ni(CO) is preferred. Any gas relatively inert'to Ni(CO) and H 8 such as H CO N and the noble gases may be employed as the carrier gas, and utilizationofi a particular gas does not appear to becritical to the successful operation of our invention. However, CO2 is generally preferred.

Since in the complete mixture of our invention the nickel carbonyl tends to decompose at roomtemperature, only the nickel carbonyl and H 8 may be premixed and stored whilethe atmospheric oxidizing agent should be added just before impingement of the resulting mixture upon the target. The latter may easily be accomplished, for example, by employing two concentric feed nozzles or two opposing feed nozzles, the nickel carbonyl vapor-H 8, mixture being supplied by one nozzle and the atmospheric oxidizing agent being supplied by the second nozzle.

The optimum distance of the feed nozzles from a surface being plated may vary with the specific nature of each surface and is best determined by trial and error methods. In any event however, the distance must be relatively short, i.e., a matter of a few inches or less, since the nickel carbonyl begins decomposing as soon as it is incorporated in the complete mixture of our invention.

We find that our invention may be satisfactorily practiced employing either laminar or turbulent gas flow conditions. The optimum flow rate in a particular plating run is subject to empirical determination and will depend upon a number of variables including the percent of Ni(CO) in the vapor mixture, the temperature of the reaction zone and the shape, size and nature of the target substance. Generally, however Reynolds numbers as low as 300 may be utilized, and in any event, employing our invention, considerably lower Reynolds numbers may be utilized than those required in the prior art for satisfactory plating.

Although we find that the inclusion of an atmospheric oxidizing agent, as herein described, permits the plating operation to be conducted at room temperature, higher temperatures may be satisfactorily employed. However, there is no advantage to be gained other than a corresponding increase in the rate of plating while the advantage of being able to plate thermally sensitive materials may be lost.

In addition, our method may also be satisfactorily employed at temperatures as low as the minimum at which a suitable percentage volume of the nickel carbonyl may be maintained in the vapor phase. However, operation at room temperature is preferred.

Thus, in a preferred form of our invention, a solid surface may be nickel plated by subjecting same to contact with a mixture containing approximately 20% nickel carbonyl vapor by volume, approximately 0.2% H 3 by Volume and approximately 0.1% water vapor by volume or approximately 1% oxygen by volume, and the remainder CO at room temperature until the desired thickness of nickel is obtained.

The following examples will illustrate our invention in greater detail.

Example I A mixture consisting of 20% Ni(CO) vapor, by volume, 0.2% H 8 by volume, 0.1% H vapor, by volume, and the remainder CO was passed through the interior of a steel pipe /2 inch in diameter, at room temperature and at a non-turbulent flow rate of approximately 0.07 c.f.m. until a coating thickness of 0.7 mil was obtained. The nickel was deposited at a rate of approximately .02 mil per minute and was smooth, bright and generally dense, and contained only about 0.02% carbon.

Example 11 The precodure of Example I was employed except that 1% oxygen by volume was substituted for the water vapor. The results were substantially similar to those of Example I.

Example 111 The procedure of Example I was employed except that neither water vapor nor oxygen was provided in the nickel carbonyl-H 8 mixture. The deposition of nickel was observed to be impracticably slow.

Example IV ing the scope of our invention which should be understood to be limited only as indicated by the appended claims.

What is claimed is:

1. An improved method of nickel plating a surface which comprises effecting contact of said surface with a mixture comprising approximately 5% to approximately 40% of nickel carbonyl vapor by volume, approximately 0.2% H 8 by volume, approximately 1% oxygen by volume and the remainder an inert carrier gas, while maintaining the surface-gasinterface during said contact at approximately ambient atmospheric temperature, until the desired thickness of nickel on said surface has been obtained.

2. An improved method of nickel plating a surface which comprises effecting contact of said surface with a mixture comprising approximately 5% to approximately 40% of nickel carbonyl vapor by volume, approximately 0.2% H 8 by volume, approximately 0.08% water vapor by volume and the remainder an inert carrier gas, while maintaining the surface-gas interface during said contact at approximately ambient atmospheric temperature, until the desired thickness of nickel on said surface has been obtained.

3. An improved method of nickel plating a surface, which comprises effecting contact of said surface with a mixture comprising approximately 5% to approximately 40% of nickel carbonyl vapor by volume, approximately 0.1% to approximately 1% H 8 by volume, approximately 0.02% to approximately 1.5% by volume of at least one atmospheric oxidizing agent selected from the group consisting of oxygen and water vapor, and the remainder an inert gas, while maintaining the surface-gas interface during said contact at approximately ambient atmospheric temperature, until the desired thickness of nickel on said surface has been obtained.

4. An improved method of nickel plating a surface, which comprises effecting contact of said surface with a mixture comprising approximately 5% to approximately 40% of nickel carbonyl vapor by volume, approximately 0.1% to approximately 1% H 8 by volume, approximately 0.5% to approximately 1.5 oxygen by volume, and the remainder an inert carrier gas, while maintaining the surface-gas interface during said contact at approximately ambient atmospheric temperature, until the desired thickness of nickel on said surface has been obtained.

5. An improved method of nickel plating a surface, which comprises effecting contact of said surface with a mixture comprising approximately 5% to approximately 40% of nickel carbonyl vapor by volume, approximately 0.02% to approximately 0.16% water vapor by volume, and the remainder an inert carrier gas, while maintaining the surface-gas interface during said contact at approxi mately ambient atmospheric temperature, until" the desired thickness of nickel on said surface has been obtained.

References Cited in the file of this patent UNITED STATES PATENTS 455,230 Mond June 30, 1891 1,759,661 Muller et a1 May 20, 1930 2,475,601 Fink July 12, 1949 2,523,461 Young et a1 Sept. 26, 1950 2,656,284 Toulmin Oct. 20, 1953 2,657,457 Toulmin Nov. 3, 1953 2,700,365 Pawlyk J an. 25, 1955 OTHER REFERENCES American Institute of Mining and Metallurgical Engineers Technical Publication No. 2259, copyright 1947, pages 35-40.

Comprehensive Treatise on Inorganic and Theoretical Chemistry by Mellor, volume 5, 1924, pages 953-956. 

1. AN IMPROVED METHOD OF NICKLE PLATING A SURFACE WHICH COMPRISES EFFECTING CONTACT OF SAID SURFACE WITH A MIXTURE COMPRISES APPROXIMATELY 5% TO APPROXIMATELY 40% OF NICKEL CARBONYL VAPOR BY VOLUME, APPROXIMATELY 0.2% H2S BY VOLUME, APPROXIMATELY 1% OXYGEN BY VOLUME AND THE REMAINDER AN INERT CARRIER GAS, WHILE MAINTAINING THE SURFACE-GAS INTERFACE DURING SAID CONTACT AT APPROXIMATELY AMBIENT ATMOSPHERIC TEMPERATURE, UNTIL THE DESIRED THICKNESS OF NICKEL ON SAID SURFACE HAS BEEN OBTAINED. 